The “unit effect” makes 31 days seem better than a month

Is it better to pay more to have something delivered in a month or 31 days? …

The human brain engages in all sorts of mental shortcuts in order to make quick judgements about the world, and some of them make us vulnerable to marketing. For example, consumers will readily attach weight to completely fictitious product statistics, preferring items with the most bogomips, even if they have no idea of what the significance of that figure is. That may be disappointing, but apparently it's even worse than that—even when they do know what the units are, people tend to prefer a bigger number. As a newly released study shows, people would rather pay for expedited service to get things in 31 days than they would to get it in one month.

The researchers involved in the new work cite an extensive list of some of the counterintuitive judgements people make when it comes to numbers. For example, we do dumb things when it comes to foreign exchange. When we shop in currencies with a favorable exchange rate, we tend to spend less, because handing over a large quantity of currency strikes us as overspending, regardless of the currency's relative value. In the same way, we tend to overspend currencies with a high value.

The authors argue that this may occur simply because we don't understand the units. It's hard to do some conversions in our heads, or we may not have all the relevant information to do them. But what happens when we do know the units—is bigger still better? The authors devised a series of tests to find out.

In the first set of tests, the authors used two different scales, either 1-10 or 1-1,000, to describe television quality and the success rate of a medical procedure; they also fed the subjects warranty lengths in either months or years. Even when the length of time was the same—seven versus nine years, or 94 versus 108 months—the subjects tended to prefer the bigger number. The same thing happened for medical procedures, where an equivalent effectiveness was preferred when it was rated on a thousand-point scale.

The same sort of thing occurred when they offered students a snack and listed its energy content in either kilocalories or a much smaller unit, the kilojoule. Depending on whether they were interested in watching their energy intake, the alternate figures had the expected impact: if you wanted fewer calories, you tended to prefer seeing things expressed in kilocalories, since that produced a smaller number.

The clearer indication of the unit effect came when the subjects were asked to consider paying for expedited service. Told there was a wait time of several months, the students were asked if they were willing to pay more to get an item in a shorter amount of time: a month or, alternately, 31 days. More students were interested in paying to get the item in 31 days; a month-long wait for delivery wasn't as appealing. All the researchers had to do was insert a reminder—tell the students that a month is roughly 31 days—and the unit effect vanished.

(The one oddity of this experiment is that the students were asked to envision waiting for an item like a CD or cell phone. Unless their hearts were set on a white iPhone, however, these sort of extended waiting times seem very artificial.)

The fact that we humans aren't especially brilliant when we make snap judgements shouldn't surprise anyone. But it is a bit of a shock that so many people seemed to need a reminder to consider that a month lasts about 31 days. The authors think that, rather than being unable to interpret the units involved (as is the case with currency), most people simply choose to ignore them entirely.

What's really striking, however, is that the researchers can't really explain why reminding anyone that a month is 31 days seems to wipe the effect out. The best guess they can offer is that it simply compels people to slow down and think a little bit.

Maybe they were avoiding the ambiguity of 31days, many times that refers to business days which is 6-7 weeks, whereas a month is 4 weeks. A theory as to why the effect disappears when there is a reminder that a month is 31days is that the reminder takes away the ambiguity.

There has got to be a difference between scientific-minded people who understand units and non-scientific people who don't. As an engineer, the first thing I was doing mentally in every example was trying to convert the two selections into common units. It was natural to me...a habit.

Completely non-science people might fall into this silly trap. One of the earlier comments, comparing 5 years and 55 months, is a much more interesting number selection. But whatever. This is a silly study, and part of me thinks they're drawing more of a conclusion than they probably should, but who really knows.

What's really striking, however, is that the researchers can't really explain why reminding anyone that a month is 31 days seems to wipe the effect out. The best guess they can offer is that it simply compels people to slow down and think a little bit.

Am I the only one who read this and thought "duh!?"

I also had a hard time understanding the setup of the experiments based on the article. I don't know if the article is poorly worded, or the study is poorly explained in the original paper, or what.

How did they gauge preferences as described in the article? Was it something like:

Quote:

Group 1: Rate the effectiveness you perceive for an operation rated 900 on a scale of between 1-10001 (not effective) - 10 (very effective)

Group 2: Rate the effectiveness you perceive for an operation rated 90 on a scale of between 1-1001 (not effective) - 10 (very effective)

...and then they found the average rating given? This is the only way I can see this study working without any sort of bias.

If you asked someone, "Which sounds better, 9/10 or 900/1000?" I sincerely hope that they couldn't answer that question directly, because the only logical answer is they're the same damn thing. Otherwise, I fear for our collective intelligence.

I know many people who would confidently say that 5 years is a shorter time period than 55 months. And some others would perhaps ask: why the choice - both are surely equal?

I hesitate to say 'not knowing maths is a tax on the stupid' - I know some 'utterly hopeless at maths' people who earn considerably more than me. They're intelligent in other ways. Enough so to be able to pay other people to do their maths for them.

In the grocery store it is more and more common to see products advertised as 10/$5.00 rather than $0.50 each even though the two are equivalent. People really do tend to buy products advertised like that in lots of ten rather than individually, even though there is no actual "bulk discount" at play.

Valid comparisons can only be made when the units of measure are the same. Scientists go to lengths to ensure that they are not making assumptions based on the different units of measure. But, of course marketers do the opposite to confuse people.

"More students were willing to pay for getting the item in a month than those who wanted to wait the same amount of time expressed as days."

So students would prefer to get things in a month over 31 days? Makes sense to me, five of the months are less than 31 days long, so students who stopped to think would pick this answer.

I think they offered some students "1 month" and other students "31 days". Students were more likely to accept the shipping charge in one scenario over the other. So I'm guessing students saw "The wait time for this is 93 days. Would you like to spend $25 to receive it in 31 days?" instead of "The wait time for this is 93 days. Would you spend $25 to receive it in 31 days or $25 to receive it in 1 month or neither?". Otherwise it seems like a really weird setup when you put those options side-by-side.

erm... not me. The longest month is 31 days, so at worst, choosing "1 month" is a wash.

Another way of interpreting the logic laid out in the article is that ONE thing sounds like a lot less than thirty-one of some other thing, even if it's known that the single thing is some 30X larger than the other things.

Maybe they were avoiding the ambiguity of 31days, many times that refers to business days which is 6-7 weeks, whereas a month is 4 weeks. A theory as to why the effect disappears when there is a reminder that a month is 31days is that the reminder takes away the ambiguity.

Some months have 31 days, some don't. Only 7 months out of the 12 monthly cycle have 31 days, and then you need to take into account leap year.

Months with 31 days: 1. January 2. March 3. May 4. July 5. August 6. October 7. December

I do like your idea of business days. That's one important thing to consider since each week of 7 days only has 5 days of actual business when it comes to shipping, in most cases.

Tolerances. If you say 31 days, if you miss it by a day, it's clear you're overdue. If we say 1 month, and I get it in 32 days, you're basically still on time and I have less ability to seek compensation. I want to be as specific as possible, which the larger number is inherently better at.

My thought process when I heard the question:"The term 'month' is vague but, because it could range anywhere from 28 to 31 days, I'll go with 'month' because it is equivalent to 31 days at worst and might be shorter."

Though I'm sure the only reason I decided to conceptualize a month in terms of a number of days was because the second option led me to look for an easy way to compare the two things. Take that, science!

I would always choose the 31 days over the 1 month, do to the precision issue. If someone says something will arrive in 31 days, I assume it will be pretty close to 31 days. However if some says it will arrive in 1 month, I'm assuming that's a rough estimate and the variance is liable to be higher.

I echo what Paltivar said above. When a time period is expressed in days, I'm going to consider it rounded to the nearest day. When the time period is expressed in months, I'm going to at least wonder if it's rounded to the nearest month. So "a month" might mean 30-31 days, or it might mean "sometime next month"... which may be significantly more than 31 days. This easily explains why the bias disappeared when the link to days was made more explicit.

Tolerances. If you say 31 days, if you miss it by a day, it's clear you're overdue. If we say 1 month, and I get it in 32 days, you're basically still on time and I have less ability to seek compensation. I want to be as specific as possible, which the larger number is inherently better at.

This. I was thinking, of course I want it in 31 days. More precision. For me, if "1 month" and "31 days" are listed separately, it may not be the case that "1 month" will be at most 31 days. However, remind me that 1 month is 31 days then I now consider your unit of 1 month to have the same precision as 31 days.

In the real world, which mechanic would you typically expect to have your car ready the quickest?

neither - In my experience, your car will be ready at the time of day originally estimated for completion + however many billable hours they are charging you.

So if you drop it off at 9am for a 2 hour job and they say it will be done at 1pm, it will really be done at 3pm.

Sure, except I wasn't really trying to say that a good mechanic is going to know down to the second when my new alternator is going to be installed.

It was more a statement about the effect specificity of a number has on social interactions. As another example, if someone tells you something will cost $1k and it actually ends up costing $1125, they really didn't lie to you and you don't have much basis to be terribly annoyed. If someone says something will cost $1001.43 and it ends up costing $1126.43, you have a much stronger basis for being annoyed and to demand that the cost be reduced.

Therefore, you're much better off going for $1001.43 than $1k; specificity (even when one value is mathematically greater) can be very valuable. Extend that "specificity is valuable" idea to identical numbers and it can make very good sense to conclude that a 24-month pledge is superior to a 2-year pledge.

In the grocery store it is more and more common to see products advertised as 10/$5.00 rather than $0.50 each even though the two are equivalent. People really do tend to buy products advertised like that in lots of ten rather than individually, even though there is no actual "bulk discount" at play.

Similarly, not just advertising that way, but putting on sale that way. Regular price $3.00, but today only, 2/$5! Yes, it's a decent sale, but it also tricks people into buying two, when the price is still valid for one unit. You *COULD* get just one for $2.50; but because you see "2/$5", you subconsciously want two because it feels like a deal the way they have it written. Heck, I know all about the effect, and I still succumb to it occasionally. (Yes, there are stores that make you buy the "advertised quantity" to get the sale, so for example in that case, just buying one would still be $3.00, it's just that the second would only be $2.00 - but for most, even when they advertise 2/$5, it's really just "$2.50 each".)

The "unit effect" on currency annoys the crap out of me... no, not that I have any trouble with it (FWIW, I've lived in several countries), but I've had far too arguments with people who that truly believe that "things are more expensive in the UK than in the US _because_ you have to pay in pounds". I've of course had the same argument in other currencies but the USD to GBP one seems most common. No argument will move these people off their errant belief that the currency you pay in directly affects the cost of something.

In the real world, which mechanic would you typically expect to have your car ready the quickest?

neither - In my experience, your car will be ready at the time of day originally estimated for completion + however many billable hours they are charging you.

So if you drop it off at 9am for a 2 hour job and they say it will be done at 1pm, it will really be done at 3pm.

Sure, except I wasn't really trying to say that a good mechanic is going to know down to the second when my new alternator is going to be installed.

It was more a statement about the effect specificity of a number has on social interactions. As another example, if someone tells you something will cost $1k and it actually ends up costing $1125, they really didn't lie to you and you don't have much basis to be terribly annoyed. If someone says something will cost $1001.43 and it ends up costing $1126.43, you have a much stronger basis for being annoyed and to demand that the cost be reduced.

Therefore, you're much better off going for $1001.43 than $1k; specificity (even when one value is mathematically greater) can be very valuable. Extend that "specificity is valuable" idea to identical numbers and it can make very good sense to conclude that a 24-month pledge is superior to a 2-year pledge.

From the article:Even when the length of time was the same—seven versus nine years, or 94 versus 108 months—the subjects tended to prefer the bigger number.

I think you mean seven years versus 94 months, or nine years versus 108 months.

Also...from the article, it seems that the study makes a glaring omission in regards to the concept of specificity. See GKH's posts in this discussion. Perhaps the subjects' decisions were not influenced by specificity, bit I surely don't trust the conclusion since the possibility was not addressed.

I am one to convert to compare also, but I would choose e.g. (31 days +/- 5 days) over (1 months +/- 0.5 months).

It is interesting to see the effect of a more precise count (in terms of significant figures) implying a more accurate count. We also shy away from fractions and decimal places, preferring the comfort of a unit number.

There seems to be an unspoken assumption that information given in terms of a unit are accurate to the nearest unit. But, when you think about it, what practical examples do we have that supports this assumption? Definitely not time - if you give someone a time on the hour, how late do you feel you can be? five minutes? Quarter of an hour? It's a bit more complex than that, and definitely not simply due to the unit.

The correlation between precision and accuracy isn't quite as strong as I'd like. For example, TRUenergy tried to bill me $832.53 despite charging me for three out-of-hours callouts that didn't happen. When I'm on the phone to them whilst waiting on the platform at Town Hall for the 8.02am train (delayed), their call centre routinely tell me I'll be serviced in under five minutes, which is misleading at best.

Perhaps you'd trust Mechanic 2 if he's got a good reputation and you've used him before, no matter to how many fractions of a millisecond he can go to with regard to when your car will be ready.

There seems to be a lot of interesting stuff for marketing departments in this article. Is there any legal consumer requirements regarding specifying a misleading degree of precision as part of a retail product or service?